Reinforcement containing carbon fibers

ABSTRACT

A textile reinforcement for integrating into concrete, having carbon fibers. The reinforcement is coated with a layer which protects against oxidation, wherein the carbon fibers are provided in the form of an interlaced, twisted, or cabled thread structure and have 5 wt. % of matrix resin, and the layer which protects against oxidation is a separate layer and can produce a chemical bond to a component of the concrete. The invention additionally relates to a concrete part which has a textile reinforcement.

The application relates to a textile reinforcement that is suitable for being completely casted in concrete and a concrete construction part, respectively.

Concrete has a tensile strength of only about 10% compared to the compressive strength. In order to increase the tensile strength of concrete, which was a new construction material at the time, people began to combine concrete with other, more tensile materials as early as the middle of the 19th century. Particularly noteworthy here are the works of the French gardener Joseph Monier, who combined concrete with iron mesh for planters. Today, Monier is regarded as the inventor of concrete fortified or reinforced with steel elements, or reinforced concrete for short. After him, the reinforcing elements cast in reinforced concrete are still colloquially called “Monier irons”. Other materials for the manufacture of reinforcements are still the subject of current research and development, in particular textile-based reinforcements.

Various fibre and textile materials are known, the tear strength of which is significantly higher than that of steel, but which are also significantly lighter than steel. Massive weight savings are therefore possible for concrete construction parts or concrete building structures, which has a positive effect on the statics of load-bearing structural elements such as bridge piers or abutments, for example. At the same time, textiles, for example, based on glass fibres, basalt fibres, carbon fibres (“carbon”, “carbon fibres”) or certain organic polymers, offer the great advantage of a lower susceptibility to corrosion, while in the case of metal reinforcements, chemical wear of the reinforcement elements can be expected over the long term, which can lead to a dangerous reduction in the load-bearing capacity of the structural elements concerned, both through failure of the reinforcement itself and through spalling of concrete due to expansion of the corroding reinforcement elements. In addition to the general oxidation sensitivity of metals, especially construction steel, it is also playing an important role that the concrete matrix in which the reinforcement elements are embedded reacts strongly alkaline and is therefore chemically very aggressive.

Textile reinforcements are still in the development phase. In 2005, for example, the world's first bridge made of textile-reinforced concrete was built on the grounds of the State Horticultural Show in Oschatz (Saxony).

Carbon fibres have turned out to be interesting for the production of textile reinforcements for concrete. Carbon fibres offer high tear strength and, at normal temperatures, are extremely resistant to environmental influences such as water, oxygen or the highly alkaline environment in concrete. Carbon fibres have a high tear strength in the direction of the fibres, but are very brittle transversely to the direction of the fibres. This disadvantage is remedied by embedding carbon fibres in a matrix resin, which absorbs the corresponding forces and ensures cohesion of the carbon fibres among each other.

The problem with textile reinforcements is their low heat resistance. Concrete construction parts with textile reinforcement are therefore unsuitable for applications in which they are permanently exposed to high temperatures. At the same time, however, a temporary resistance to high temperatures must be guaranteed in order to ensure the stability of concrete construction parts with textile reinforcements in the event of a fire. A temporary resistance to high temperatures in the event of a fire is referred to as “fire resistance”. It is based on the length of time a construction part retains its function in the event of a fire. A common requirement for building structures at risk of fire is the fire resistance class “F90 fire-resistant” (functional for at least 90 minutes in the event of a fire). With conventional reinforced concrete construction, protection for 90 minutes is achieved primarily with a sufficiently large concrete cover.

WO 2018/202785 discloses a concrete construction part with textile reinforcement, which has an improved resistance in case of a fire, which is brought about by the concrete being modified accordingly in order to prevent spalling, inorganically dominated matrix materials being used for the reinforcement or the reinforcement being surrounded by an oxidation barrier that protects the fibres from exposure to oxygen.

The disadvantage of the state of the art, however, is that the fibres in the textile reinforcement are still held together by a binder that has organic proportions that form gases under the influence of intense heat, thus burst the surrounding concrete and cause the construction part to collapse.

It is the object of the present invention to provide a textile reinforcement which is outstandingly fire-resistant and at the same time simple to produce.

The object is achieved by a textile reinforcement for embedding in concrete, having carbon fibres, wherein the reinforcement is coated with a layer protecting against oxidation, wherein the carbon fibres are present as an interlaced, intertwined, twisted or cabled thread-like structure and have a maximum of 5 wt. % of a matrix resin, and the layer protecting against oxidation forms a separate layer and can produce a chemical bond to a component of concrete.

The present invention relates to a reinforcement. It should be made clear that the term “reinforcement” always means that a material (namely the reinforcement) is cast or embedded in another material (that is to be reinforced). A textile reinforcement that is to be embedded in concrete (as required in claim 1) means here that at least the upper surface and the lower surface of the textile reinforcement—which extend as surfaces in the longitudinal extent of the reinforcement and run essentially parallel to one another—are almost completely covered by concrete (see FIG. 10 ). The present textile reinforcement is thus enclosed (with the exception of edge areas) by concrete at least on the upper and lower surfaces. A material placed on top of concrete and not enclosed by concrete is not a reinforcement.

A separate layer protecting against oxidation should be understood to mean a layer that lies essentially completely around the reinforcement as an outer surface or coating. The layer protecting against oxidation is preferably present in the form of a substantially complete coating of the reinforcement. A substantially complete coating of the reinforcement means that less than 30% of the outer surface, less than 20% of the outer surface, less than 10% of the outer surface or less than 5% of the outer surface of the reinforcement is free of the layer protecting against oxidation. The layer protecting against oxidation can have isolated cracks. A separate layer protecting against oxidation consists essentially entirely of the material protecting against oxidation, this means preferably to over 75 wt. %, more preferably to over 80 wt. %, even more preferably to over 90 wt. % and most preferably to over 98 wt. %. According to the invention, the carbon fibres that form the thread-like structure of the reinforcement consequently have no more than 5 wt. % of matrix resin and the reinforcement is surrounded by a separate layer protecting against oxidation.

There is no separate layer protecting against oxidation within the meaning of the invention if the material protecting against oxidation is present only sporadically and not as a full-surface coating on the reinforcement or on the carbon fibres or on the thread-like structure. There is also no separate layer protecting against oxidation if the substances protecting against oxidation are merely admixed as additives in a matrix material for coating the reinforcement or the fibres of the reinforcement.

The weight proportion of the separate layer protecting against oxidation is less than 15 wt. %, preferably less than 10 wt. %, more preferably less than 7.5 wt. % and most preferably less than 3 wt. %, based on the total weight of the textile reinforcement.

Document EP 0 861 862 describes a method for reinforcing structures. In this case, for example, a concrete layer is to be reinforced by applying a fibre layer to the surface of the concrete layer. The fibre layer is used together with a primer layer and a putty layer and is impregnated with a resin. The fibre layer is not set in concrete. Consequently, the document does not describe a reinforcement either. Furthermore, the document does not describe carbon fibres which are in the form of an interlaced, intertwined, twisted or cabled thread-like structure or carbon fibres which contain at most 5 wt. % of a matrix resin. A separate layer protecting against oxidation is also not disclosed in the document. Document WO 2015/084720 describes an adhesive tape material which can be used for the external repair of construction parts (see FIGS. 1 to 4 of the document). The material is not embedded in concrete and therefore no reinforcement is described in this document. The material has reinforcing fibres embedded in a matrix material. There is no reference to carbon fibres present as interlaced, intertwined, twisted or cabled thread-like structures. A separate layer protecting against oxidation is also not disclosed. The document WO 2019/091832 describes a fibre product with a coating of aqueous polymer dispersion, the use of which is specified, for example, as reinforcement in concrete. According to the examples, the entire textile formed is impregnated with a polymeric material for this purpose, so that the coating of polymeric material encloses as many individual filaments of the textile as possible, thus enabling an internal bond between the fibres. The document further describes the use of inorganic thickeners, which can be used as additives in the aqueous dispersion. A separate layer of the reinforcement protecting against oxidation is not disclosed in the document.

The layer protecting against oxidation is preferably applied via a water-based system, for example, an aqueous dispersion. All common textile coating methods—in the case of a layer protecting against oxidation made of vermiculite, for example, immersing the reinforcement in an aqueous dispersion of the coating agent—could be used. A sol-gel method (here, inorganic and hybrid polymer layers can be produced from colloidally disperse solutions by wet-chemical coating methods and subsequent hardening) or a galvanic method could be used.

An advantage of an aqueous dispersion for forming the layer protecting against oxidation is that it can be processed without a solvent (with the exception of water as the solvent), which makes processing much easier (also with regard to occupational safety and environmental protection).

In a general embodiment, means for increasing stability and/or abrasion resistance can also be added to the layer protecting against oxidation. For example, the layer protecting against oxidation can have 80 wt. % of substances protecting against oxidation and at most 20 wt. % of a water-soluble protective polymer, such as the one that can also be used for the further protective layer described later. The protective polymer should act as a binder and can, for example, stiffen a vermiculite layer (as an embodiment of the layer protecting against oxidation), so that the mechanical strength will be increased. Furthermore, the mechanical resilience of a vermiculite layer (as an embodiment of the layer protecting against oxidation) and its connection to the thread-like structure can be improved by mixing it with binders. This creates a mixture of substances and binders that protect against oxidation and therefore no additional layer. Epoxy resins and phenolic resins, for example, can be used as organic binders for the layer protecting against oxidation. The mechanical strength of the layer protecting against oxidation, for example, a vermiculite layer, can also be increased by mixing the layer protecting against oxidation (or its components) with particularly heat-resistant polymers such as bismaleimidazole, phenolic, cyanate ester or polybenzimidazole resins. Carbon-based materials such as graphene and graphene oxide, silicon-based materials such as polysiloxanes or silicone resins, colloidal silica or nanosilica, microsilica or other inorganic materials such as e.g. ZnO nanoparticles (e.g. NANOBYK-3860, Fa. BYK, Wesel, Germany), lime, cement, anhydrite, ettringite, silica sol and water glass can be used as a binder in the layer protecting against oxidation to improve the properties of the layer. The layer protecting against oxidation can also have polyelectrolytes such as polycarboxylate ethers or lignin sulfonate, cellulose ethers such as methyl cellulose, polyvinyl alcohol or polyvinylpyrrolidone. For all the admixtures mentioned, that are present in the layer protecting against oxidation, it should however be noted that the material protecting against oxidation remains the main component of the layer and the admixtures also do not result in forming an additional layer of these admixtures in the layer protecting against oxidation.

Advantageously, the textile reinforcement has a proportion of organic substance that is so low that the formation of gaseous decomposition products during heating is no longer significant and the construction part cannot be blown up in the event of a fire. The skilled person knows, for example, that no fire resistance tests are required for concrete construction parts with an organic proportion of less than 1 wt. %. With steel reinforcements, the concrete covering of the reinforcement elements must ensure that the reinforcement does not heat up to more than 550° C., otherwise the steel would lose its strength. Carbon fibres, on the other hand, are stable at this temperature in the absence of oxygen and thus allow a smaller concrete cover, which results in significant weight savings.

A textile reinforcement within the meaning of the present application is a material based on thread-like structures that is embedded in a surrounding material, for example, concrete, for reinforcement. The thread-like structures can be present as threads in the narrower sense, but they can also be products made from threads. Possible products are, for example, yarns, cables, cords or ropes, which can also be processed into flat products such as woven fabrics, scrims, crocheted fabrics, braids, warp-knitted fabrics, trebles, grids or nets. The textile reinforcements produced in this way are characterized by their flexibility, which makes it possible to store the textile reinforcement in a space-saving manner, e.g. in roll form, and to transport it to the construction site and only unroll it immediately before setting it in concrete. Rigid reinforcement elements such as rods or rigid lattices can also be produced by using binding agents or by appropriately intertwining and/or interlacing of the thread-like structures. So-called wrapping yarns, with which the thread-like structures or the yarns, cables, cords or ropes made from them are wrapped or braided, can also mechanically stiffen the thread-like structures, the yarns, cables, cords, ropes, woven fabrics, scrims, crocheted fabrics, braids, warp-knitted fabrics, trebles, grids or nets made from them.

In an embodiment, the textile reinforcement consists of the thread-like structures mentioned.

In an embodiment, the reinforcement has a (further) protective layer in addition to the layer protecting against oxidation. The protective layer is preferably located as an outer layer on the finished reinforcement with the separate layer protecting against oxidation and preferably not over the entire surface around the thread-like structure of the carbon fibres. The protective layer preferably covers the upper surface and/or the lower surface of the reinforcement. The protective layer can be a coating, for example, which makes it possible to (better) wind up the reinforcement and thus store it as rolled goods. The protective layer can also be composed of or contain substances that simplify and/or improve the embedding of the reinforcement in the concrete. For example, the protective layer can contain flow agents for concrete. Furthermore, the protective layer can also protect the reinforcement from the weather and/or mechanical loads as long as it has not yet been installed in the concrete. The protective layer can be provided reversible or fixed to the reinforcement. A reversible protective layer is present if the protective layer can be pulled off the reinforcement, for example, as a type of foil. In this case, all types of polymer films are conceivable as films, wherein it is also possible for the polymer film to be water-insoluble (for example, a polyethylene film). The protective layer is firmly connected to the reinforcement if the protective layer and the reinforcement can no longer be detached from one another without destroying the reinforcement. In the case of a protective layer being firmly connected to the reinforcement, the protective layer is preferably designed to be water-soluble, so that it dissolves in the concrete on contact with the water. In this way, the protective layer can protect the reinforcement prior to being set in concrete in, but it does not prevent or worsen the penetration of the reinforcement with the concrete. The protective layer can include or consist of, for example, polyelectrolytes such as polycarboxylate ethers or lignin sulfonate, cellulose ethers such as methyl cellulose, polyvinyl alcohol or polyvinylpyrrolidone. The reinforcement preferably has about 1 to 10 wt. %, preferably 2 to 5 wt. % of the protective layer, based on the total weight of the reinforcement.

In an embodiment, the textile reinforcement has more than one thread-like structure. In an embodiment, the textile reinforcement consists of more than one thread-like structure. The individual thread-like structures of the reinforcement can be interlaced, twisted, intertwined or cabled. In addition to one or more thread-like structures made of carbon fibres, the textile reinforcement according to the present application can also contain additional thread-like structures made of other fibres. Thread-like structures such as polyamide fibres, aramide fibres, alkali-resistant glass fibres (AR glass fibres), basalt fibres, polypropylene fibres, polyvinyl alcohol fibres, polyester fibres or fibres made of oxidized, infusible polyacrylonitrile (e.g. Pyromex®, available from Teijin Carbon Europe, Wuppertal, Germany) are particularly suitable for this purpose. In an embodiment, the additional thread-like structure of the reinforcement is a plurality of wrapping threads with which the thread-like structure made of carbon fibres is wrapped. The wrapping can, for example, increase the mechanical stability of the thread-like structure made of carbon fibres and thus of the reinforcement. The wrapping can take place uniformly over the entire reinforcement or there is only a wrapping in partial areas of the reinforcement. For example, only a central area of the reinforcement can be particularly mechanically reinforced by means of the wrapping threads.

In an embodiment, the thread-like structure has a structured surface due to its production by interlacing, intertwining, twisting or cabling. This structured surface makes it possible to bring the thread-like structure into a particularly intimate form-fitting connection with other materials, for example, coatings, the layer protecting against oxidation, the further protective layer or concrete. In an embodiment of the wrapping threads, the wrapping threads produce a structured surface in addition to the mechanical reinforcement or without mechanical reinforcement and thus enable an intimate form-fitting connection—as described above.

By interlacing, intertwining, twisting, wrapping or cabling, the carbon fibres and/or filaments are held together in the thread-like structure, which makes it possible to significantly reduce or even completely eliminate the proportion of a matrix resin required to hold the fibres together within the thread-like structure. If only one thread-like structure is used, the endless filaments that make up this thread-like structure are intimately connected to one another by interlacing, intertwining, twisting, wrapping or cabling. If several thread-like structures are used, several thread-like structures can be intimately connected to one another by interlacing, intertwining, twisting, wrapping or cabling, optionally also in addition to an intimate connection of the filaments making up the thread-like structures.

A major disadvantage of the matrix resin is its problematic behaviour at high temperatures. In the case of significantly higher temperatures, the matrix resin begins to soften and can no longer ensure the cohesion of the carbon fibres among each other and can no longer compensate for the brittleness of the carbon fibres transverse to the fibre direction. In addition, it begins to decompose, even in the absence of air, with the formation of gaseous products, which can then burst the surrounding concrete. At high temperatures and oxygen access, carbon fibres can also oxidize themselves, while in the absence of oxygen they are stable even under extremely high temperatures.

In this way, a significant contribution is made to the better fire resistance of the carbon fibre-based textile reinforcements, since the cohesion within the thread-like structure is no longer achieved by a matrix resin that quickly fails when the temperature increases, but mechanically by the intertwining of the fibres and/or filaments that make up the thread-like structure. By reducing the amount of matrix resin, the amount of thermally decomposable material in the thread-like structures can also be reduced, so that gas formation under the influence of high temperatures is minimized or eliminated. This is accompanied by a reduction in the risk of structural failure of concrete parts provided with carbon fibre-based reinforcements due to bursting in the event of fire.

In the present application, matrix resin is understood to mean the entirety of all non-fibre-forming materials with which the carbon fibres, the thread-like structures made from them or the textile reinforcement made from them are provided before the layer protecting against oxidation is applied to the reinforcement. In particular, this means finishing agents that are applied with the aim of improving the processability of the fibres or thread-like structures, for example, means to prevent breakage, to reduce static charging or to improve the slippage of the fibres during processing. Such fibre finishes are known to a skilled person as “sizing” or “size”. Organic synthetic resins such as epoxy resins or polyurethane-based resins are often used for this purpose. A reactive polydimethylsiloxane (e.g. SILRES BS 1042, available from Fa. Wacker, Munich, Germany) can also be used as sizing. In the event that a particularly temperature-resistant finish is necessary, particularly temperature-resistant polymers such as polyphenylene sulphide (PPS), polyetherketones such as polyetheretherketone (PEEK) or polyimides such as polyetherimides can also be used. In addition, high temperature resins such as bismaleimide, phenolic, cyanate ester or polybenzimidazole resins can be used. Carbon-based materials such as graphene and graphene oxide can also be used, as can silicon-based materials such as colloidal silica or nanosilica (based on sol-gel processes; e.g. LUDOX SM 30 from the company W. R. Grace & Co.-Conn., Columbia, USA), microsilica (e.g. EMSAC 500 SE from the company Ha-Be Betonchemie GmbH & Co. KG, Hameln, Germany). In addition, other inorganic materials in conjunction with water-soluble organic polymers such as, for example, polyvinyl alcohol or polyvinylpyrrolidone can be used as a binder. In the examples given, the binders are water-soluble and are distributed accordingly in the concrete. Ferrofluids containing paramagnetic iron can act as radical scavengers and thus as oxidation inhibitors. In addition, ZnO nanoparticles (e.g. NANOBYK-3860, from Fa. BYK, Wesel, Germany), polysiloxanes or silicone resins or inorganic lubricants based on molybdenum sulphide and/or graphite (e.g. MOLYKOTE 7400 Anti-Friction Coating from DuPont, Wilmington, USA) or so-called ORMOCERE, organically modified ceramics (e.g. InnoSolTEX technology from Fraunhofer ISC, Würzburg, Germany) are suitable. Other inorganic finishes, for example, based on phyllosilicates such as vermiculite, can also be used.

In addition to the mechanical properties of the fibres, the finishing agent can also provide better binding to other parts of the matrix resin, for example, to binders. In addition to finishing agents that improve the processability of the carbon fibres or the thread-like structures made from them, the term “matrix resin” also includes binders that provide cohesion of the carbon fibres or thread-like structures among each other, but which also compensate the brittleness of the carbon fibres transversely to the fibre direction or, where appropriate, stiffen the thread-like structures or the yarns, cables, cords or ropes made from the thread-like structures into rods or stiffen the woven fabrics, scrims, crocheted fabrics, braids, warp-knitted fabrics or trebles into rigid lattices. In addition, binders prevent uncontrolled penetration of concrete into the material of the textile reinforcement. This would mean that there could be telescopic pull-out of fibres from the textile reinforcement, wherein inner fibres or filaments that are not in contact with concrete can be pulled out more easily than further outwards positioned fibres or filaments that are in contact with concrete. Under “uncontrolled penetration”, a penetration of the concrete between the filaments that build up the thread-like structure is specifically considered. Otherwise, the formation of needle-shaped crystallites when the concrete hardens can destroy or damage the filaments of the thread-like structure. By an intimate connection of the filaments of a thread-like structure among each other and by an intimate connection of several thread-like structures e.g. by interlacing, intertwining, twisting, wrapping or cabling, the penetrability through concrete can be drastically reduced. Binders for thread-like structures made of carbon fibres are known to the skilled person under the designations “impregnation” or “impregnation mass”. Binders from the substance group of organic polymers are often used, which can be chemically related to the finishing agent of the fibres. As possible binders, in particular thermally or radically curable organic synthetic resins such as epoxy resins or acrylates and rubbers such as styrene-butadiene rubber or carboxylated styrene-butadiene rubber should be mentioned. In order to achieve the highest possible temperature resistance of the matrix resin, it is also possible to use inorganic binders based on silicates or cements. The use of silicone resins is also possible. Organopolysiloxanes, in particular silicone resins, such as in particular the group of methyl resins and methylphenyl resins, such as siloxanes substituted with methyl-phenyl-vinyl and hydrogen groups, and mixtures of the relevant silicone resins and organic resins have proven to be suitable. Although no basic alkali resistance is to be expected with organosilicon compounds, this was surprisingly demonstrated with some formulations (e.g. Wacker Silres H62C and in combination with Silres MK, both available from Fa. Wacker, Munich, Germany) for the special application of textile reinforcement. In the case of methyl-phenyl-vinyl-hydrogen-polysiloxanes (e.g. Wacker Silres H62C, available from Fa. Wacker, Munich, Germany), methyl-polysiloxanes (e.g. Wacker Silres MK, available from Fa. Wacker, Munich, Germany) and, in particular, suitable mixtures from these two siloxanes a surprisingly high alkali resistance has already been demonstrated in the field of textile reinforcement. Reactive polydimethylsiloxanes (e.g. SILRES BS 1042, available from Fa. Wacker, Munich, Germany) have also proved their worth. Inorganic binders with an organic proportion, in particular predominantly inorganic binders that also have an organic proportion, still tend to form a porous structure or microcracks in the high temperature range between 500° C. and 1000° C., despite their significantly better high-temperature resistance. For this reason, it is desirable to minimize the amount of binder used in the reinforcement for use in high temperature concrete parts.

A total proportion of not more than 5 wt. % matrix resin mass based on the entire reinforcement is preferred for this reason in order to achieve the best possible high-temperature resistance of the concrete parts containing a textile reinforcement corresponding to the present application. As matrix resin mass, the same material as described above for the matrix resin can be used, but this time the matrix material can be present as a component not only on the carbon fibres but also in other layers of the reinforcement. The matrix resin mass thus comprises the matrix resin of the carbon fibres and other matrix components of the reinforcement in other layers of the reinforcement. The textile reinforcement can have a maximum of 4 wt. % matrix resin mass. The textile reinforcement can have a maximum of 3 wt. % matrix resin mass. The textile reinforcement can have a maximum of 2 wt. % matrix resin mass. The textile reinforcement can have a maximum of 1 wt. % matrix resin mass. In an embodiment, the textile reinforcement is free of matrix resin mass. The binder proportion of the textile reinforcement can be 5 wt. %, 4 wt. %, 3 wt. %, 2 wt. %, 1 wt. %, or the textile reinforcement can be free of binders. It is also possible to reduce the proportion of finishing agent on the carbon fibres. Proportions of less than 1.5 wt. %, less than 1 wt. % or even less than 0.5 wt. % are possible here. In an embodiment, the carbon fibres and also the textile reinforcement are free of finishing agent.

In contrast to the matrix resin, which is particularly affected by thermal decomposition in its organic proportions in the event of a fire, the carbon fibres are largely stable at high temperatures as long as they are kept away from oxygen. For this reason, according to the present application, the reinforcement is coated with a separate layer protecting against oxidation. In principle, all materials that do not react with oxygen even under the influence of high temperatures are suitable for this layer. This is particularly the case with inorganic compounds.

In an embodiment, the layer protecting against oxidation therefore has a proportion of inorganic material of at least 80 wt. %. In an embodiment, the layer protecting against oxidation therefore has a proportion of inorganic material of at least 70 wt. %. In an embodiment, the layer protecting against oxidation therefore has a proportion of inorganic material of at least 60 wt. %. In an embodiment, the layer protecting against oxidation therefore has a proportion of inorganic material of at least 50 wt. %. In an embodiment, the layer protecting against oxidation therefore has a proportion of inorganic material of at least 40 wt. %. Particularly suitable are oxidic materials or materials whose components are oxidized to a high degree as long as they do not themselves have an oxidizing effect. Materials based on stable metal and semi-metal oxides, such as the oxides of calcium, magnesium, aluminium and silicon, are of particular importance. The oxides of these elements are characterized by high oxidation stability and a low oxidation effect as well as easy availability. Materials derived from these oxides are, for example, quartz, clay, cement or the large group of substances called silicates, in which the elements mentioned can be associated with other elements in their oxidized forms, for example, with iron or alkali metals.

What is special about this selection is that all of these materials have a high chemical similarity to certain components of concrete, such as cement. This chemical similarity enables a chemical bond to form between the material of the layer protecting against oxidation and certain components of concrete, allowing for a particularly strong adhesion between the layer protecting against oxidation of the textile reinforcement and the surrounding concrete of a concrete construction part.

In an embodiment, the layer protecting against oxidation has ORMOCERE, i.e. an organically modified ceramic (e.g. InnoSolTEX technology from Fraunhofer ISO, Würzburg, Germany), or polysilazanes.

In an embodiment, the layer protecting against oxidation therefore contains at least 5 wt. % silicon. This can include silicon-oxygen compounds such as silicates or silicones. Silicon-oxygen compounds are characterized by a particularly high chemical stability. In particular, due to the high chemical affinity of silicon for oxygen, silicon-oxygen compounds are extremely stable against reduction, do not give off oxygen even under the conditions of a fire, and accordingly do not change chemically. For example, the skilled person knows that various silicon-oxygen compounds are used as fire extinguishing agents. An important example of this is sand (chemically mostly silica, SiO2), which can be used to cover fires. Phyllosilicates such as vermiculite can also be used as fire extinguishing agents.

The layer protecting against oxidation lies on and around the reinforcement and can be present on and around the textile reinforcement in many different ways. For example, it is conceivable to produce the layer protecting against oxidation by means of a plasma treatment. In a plasma treatment, the object to be treated is exposed to a plasma to which a gaseous precursor for the desired surface coating is added. For example, a plasma treatment in the presence of hexamethyldisiloxane as a precursor leads to the formation of a layer containing silicon-oxygen compounds on the treated surface, here on the surface of the textile reinforcement. The silicon-oxygen compounds can be silicon dioxide, for example. Layers of amorphous silicates or polymer layers containing silanol groups are also possible. In an embodiment, the layer containing silicon-oxygen compounds consists of at least 30 wt. % silicon dioxide. In an embodiment, the layer containing silicon-oxygen compounds has silanol groups on its surface.

In an embodiment, the layer containing silicon-oxygen compounds has a thickness of less than 500 nanometres and is therefore significantly thinner than conventional layers protecting against oxidation. In an embodiment, the layer containing silicon-oxygen compounds has a thickness of less than 300 nanometres. In an embodiment, the layer containing silicon-oxygen compounds has a thickness of less than 100 nanometres. In an embodiment, the layer containing silicon-oxygen compounds has a thickness of less than 50 nanometres, less than 30 nanometres.

This also results in a high flexibility of the reinforcement compared to other layers protecting against oxidation. In this embodiment, the textile reinforcement retains its drapability even when coated with the layer protecting against oxidation. It is therefore possible to bring them into a desired shape immediately before setting them into concrete and, for example, to produce curved or bent concrete construction parts with little effort. The layer containing silicon-oxygen compounds can be chemically bonded to the carbon fibres themselves or to the finishing agent applied to the carbon fibres and in turn allows chemical bonding to components of concrete, e.g. to cement.

Silicates, which can be applied to the reinforcement by wet-chemical methods, for example, can also be used as a material for the layer protecting against oxidation. In this context, for example, phyllosilicates should be mentioned, which are able to form flexible, inorganic films. Inorganic films made from vermiculite have excellent mechanical properties (for example, related to tensile strength and tensile modulus) and are superior to some organic films.

In an embodiment, a flexible layer protecting against oxidation is formed by the phyllosilicate vermiculite. This is particularly the case when vermiculite is applied to a surface in the form of an aqueous suspension and then dried. Such dispersions are available, for example, under the name AVD (Aqueous Vermiculite Dispersion), inter alia as fire extinguishing agents. The layer of phyllosilicates protecting against oxidation can be anchored in the structured surface of the reinforcement with a form fit. For this purpose, for example, the phyllosilicate applied in the form of an aqueous suspension can form a structure that engages with the structure on the surface of the thread-like structure or the carbon fibres and thus ensures an intimate connection between the thread-like structure or the carbon fibres and the layer protecting against oxidation. For example, after it has been produced from the thread-like structure of carbon fibres, the reinforcement can be soaked in an aqueous suspension of phyllosilicate in an immersion bath, so that a separate layer protecting against oxidation is formed on and around the reinforcement (i.e. the outer surfaces of the reinforcement).

Optionally, an adhesive layer can also be used in addition, which ensures a chemical bond between the thread-like structure and the layer protecting against oxidation, such as the phyllosilicate. Both direct chemical bonds between the carbon fibres of the layer protecting against oxidation, such as the phyllosilicate, and chemical bonds between the finishing agent on the carbon fibres and the layer protecting against oxidation are conceivable. If epoxy resins are used as finishing agents, organically functionalized silanes with amino or epoxy groups can be used for the adhesive layer, which can form a chemical bond with the epoxy resin using their organic ends, while the silane groups form a chemical bond with the layer protecting against oxidation, such as, for example, the phyllosilicate. Possible products are, for example, (Dynasylan SIVO 110 and Dynasylan HYDROSIL 2776, both available from Evonik AG, Essen). Organically functionalized silanes mediate a chemical bond between the finishing agent (particularly epoxy resin) on the carbon fibre on the one hand and the phyllosilicate on the other hand. The adhesive layer is preferably applied to the reinforcement, that is, the thread-like structure made of interlaced, intertwined, twisted or cabled carbon fibres has the adhesive layer. In another embodiment, however, it is also conceivable for the carbon fibres to have the adhesive layer prior to the production of the thread-like structure. If an adhesive layer is used, the adhesive layer makes up less than 3 wt. %, preferably less than 2 wt. % and even more preferably less than 1.5 wt. %, even more preferably still less than 1 wt. %, based on the total weight of the reinforcement in all embodiments.

In an embodiment, the phyllosilicate layer has a maximum thickness of 200 μm. In an embodiment, the phyllosilicate layer has a maximum thickness of 150 μm. In an embodiment, the phyllosilicate layer has a maximum thickness of 100 μm. In an embodiment, the phyllosilicate layer has a maximum thickness of 75 μm. In an embodiment, the phyllosilicate layer has a maximum thickness of 50 μm. In an embodiment, the phyllosilicate layer has a maximum thickness of 40 μm. In an embodiment, the phyllosilicate layer has a maximum thickness of 30 μm. In an embodiment, the phyllosilicate layer has a maximum thickness of 20 μm. In an embodiment, the phyllosilicate layer has a maximum thickness of 10 μm.

The phyllosilicate layer can be of uniform or non-uniform thickness on and around the reinforcement.

In all embodiments of the textile reinforcement, the proportion of organic substances in all of the layers that are not reversibly and directly or indirectly (via a layer) connected to the reinforcement is preferably less than 5 wt. % based on the total weight of the textile reinforcement, wherein the thread-like structure made of carbon fibres is not counted as a layer. This means that even if the reinforcement has fibres with a sizing (matrix), a separate layer protecting against oxidation, an adhesive layer and another protective layer that is not reversibly connected to the reinforcement, the reinforcement has less than 5 wt. % of organic substances in total, related to the total weight of the textile reinforcement.

The present application also relates to a concrete construction part that has a reinforcement according to the present application. In an embodiment, the textile reinforcement is embedded in the concrete construction part in such a way that it has a concrete cover of at most 10 millimetres. The concrete cover is understood to mean the thickness of the concrete layer that is located at least between the concrete surface and the surface of the textile reinforcement. In an embodiment, the reinforcement in the concrete part has a concrete cover of at most 15 millimetres. In an embodiment, the reinforcement in the concrete part has a concrete cover of at most 20 millimetres. In an embodiment, the reinforcement in the concrete part has a concrete cover of at most 25 millimetres. In an embodiment, the reinforcement in the concrete part has a concrete cover of at most 30 millimetres. In an embodiment, the reinforcement in the concrete part has a concrete cover of at most 35 millimetres. In an embodiment, the reinforcement in the concrete part has a concrete cover of at most 40 millimetres. In an embodiment, the reinforcement in the concrete part has a concrete cover of at most 45 millimetres. In an embodiment, the reinforcement in the concrete part has a concrete cover of at most 50 millimetres. In an embodiment, the concrete cover of the textile reinforcement is lower than the concrete cover of a comparable steel reinforcement with the same mechanical properties, which means a significant weight advantage. The concrete cover of the textile reinforcement makes a decisive contribution to the fire resistance of the textile reinforcement due to its heat-insulating and oxygen-protecting effect.

The concrete cover of the textile reinforcement can be designed in interaction with the composition and the layer thickness of the layer protecting against oxidation in such a way that a desired fire resistance class is achieved.

The invention is described in more detail based on tests and figures, which should be understood as not limiting the general spirit of the invention.

FIG. 1 represents a comparison of the tensile strength of carbon fibre yarns with a solid matrix resin proportion as a function of their intertwining (t/m).

FIG. 2 shows the influence of a vermiculite coating on the temperature resistance of carbon fibres.

FIG. 3 shows the basic structure of a single-thread coating facility

FIG. 4 shows the schematic diagram of a coating eyelet (on the right side in the cross-section)

FIG. 5 shows the schematic diagram of a winding board

FIG. 6 shows a heating curve of a muffle furnace for the yarn specimens

FIG. 7 shows a target position of yarn strands for example 3

FIG. 8 shows the installed yarn strands for example 3

FIG. 9 shows a test setup (rotated) for example 3

FIG. 10 schematically shows a textile reinforcement that is embedded in concrete.

FIGS. 7 to 9 originate from the reports of the TU Dortmund/WdB.

EXAMPLE 1

In the present example 1 it is to be explained how the tensile strength of thread-like structures changes as a function of their consolidation. The thread-like structures to be tested are carbon fibre yarns of the type STS40 F13 24K from the company Teijin Carbon Europe with 1600 tex and 1% polyurethane coating as matrix resin proportion. An STS40 E23 24K yarn from the company Teijin Carbon Europe, which was thoroughly impregnated with 39 wt. % of epoxy-based matrix resin, is selected as the comparison yarn.

The comparison yarn was impregnated with the following resin mixture:

Epicote 828: 100 parts

Epicure 113: 30 parts

Acetone: 15 parts

Specimen Preparation:

For the tensile test and determination of the data, yarn specimens are provided with 50 mm long cardboard strips, which are used to introduce a force at the test device.

For this purpose, a two-component adhesive is used which, after curing, completely encloses the specimens in the area of a cardboard strip and there are no air pockets.

Adhesive formulation: AW 106 100 weight proportion

-   -   HV 953 80 weight proportion

A pot life of 45 minutes is referred to.

To prepare yarn tension test specimens, two cardboard strips, which are aligned parallel to one another using a 200 mm wide template, are firmly glued to a glass plate covered with PTFE glass using polyester adhesive tape. In order to ensure an even adhesive film between the cardboard strips and test specimens, these are applied in advance using a drawing body (which is to be selected depending on the yarn count).

The specimens are now to be placed along the marking lines and to be fixed with polyester adhesive tape. It is important to ensure that there is parallelism between the individual test specimens. The upper cardboard strips (provided with clear labelling), which are also provided with an adhesive film, are placed and fixed on these. On top of that comes a layer of PTFE glass fabric, which is weighed down with a second glass plate.

This setup is left in a preheated forced air oven at 70° C. for one hour. After cooling of the yarn tension test specimens, they are to be cut with a band saw along the outer edges and along the provided dividing lines.

Measurement:

The specimens are stored prior to the measurement in the test room climate at 23° C./50% rel. humidity for at least 24 hours.

A tensile test using an extensometer is carried out on the impregnated carbon fibre strand, which is provided with force introduction elements on both sides (cardboard glue-on).

Device:

-   -   Tensile/compression testing machine with a constant test speed         that can be set with an accuracy of <1% in the range of 0<v 20         mm/min     -   Calibrated force transducer with suitable force measuring range         according to DIN EN ISO 7500-1     -   Calibrated path measuring system with suitable path measuring         range DIN EN ISO 9531     -   Extensometer (211 mm)

Test Condition:

Standard atmosphere for testing impregnated yarn tension specimens, i.e. 23° C.±2 and 50%±5 relative humidity.

Test Parameters:

Test speed: 5 mm/min

Free clamping length: 200 mm

Preload: 2 cN/tex

Measuring length probe: 100 mm

Start modulus of elasticity: 40 cN/tex

End modulus of elasticity: 80 cN/tex

Carrying Out the Test:

The test is carried out as follows:

The tension clamps are installed in the material testing machine (MPM), aligned centrically and the required clamping length between the tension clamps is set as specified in the required standard or specification. The specimen stops are then set in such a way that the specimens are loaded centrally in the MPM. During clamping, it needs to be ensured that the specimens are clamped perpendicular to the clamping jaws.

Before the start of the test, the zero point of the force channel is approached. During the test, the testing machine drives until a fracture occurs or until the specified force or length change value is reached while recording the measured values. After the testing operation is completed, the fracture pattern is entered and the measurement data are saved. The specimen is removed from the test space and the device as well as the clamps are cleaned. In order to ensure clear traceability of the test specimens even after the test, the test specimen numbering is checked and, if necessary, renewed on both sides. The traverse of the MPM is returned to the starting position and the next specimen can be tested. According to this method, six tests are carried out per specimen.

Determination of the Tensile Strength σ_(B):

$\sigma_{B} = {\frac{F_{\max}}{A_{F}}\left\lbrack {N/{mm}^{2}} \right\rbrack}$

σ_(B)=tensile strength in N/mm²

F_(max)=maximum tensile force in N

AF=yarn cross-sectional area in mm²

The yarn cross-sectional area is calculated as follows:

$A_{F} = {\frac{T_{t}}{p \cdot \text{?}}\left\lbrack {mm}^{2} \right\rbrack}$ ?indicates text missing or illegible when filed

AF=yarn cross-sectional area in mm²

T_(t)=yarn count in tex

ρ=yarn density in g/cm³

Yarn count and yarn density were taken from the yarn data sheets and were not additionally determined by measurement.

Elongation at Maximum Force:

$\text{?} = {\frac{\Delta L_{{Fmax} \times 100}}{L_{0}}\lbrack\%\rbrack}$ ?indicates text missing or illegible when filed

ε_(B)=relative change in length in %

ΔL₀=absolute change in length at maximum force in mm

l₀=measuring length of the extensometer in mm

Modulus of Elasticity:

$E = {\rho \times \frac{\Delta F \times 10^{3}}{T_{t}} \times {\frac{\text{?}}{\Delta l}\left\lbrack {N/{mm}} \right\rbrack}}$ ?indicates text missing or illegible when filed

E=modulus of elasticity in N/mm²

ρ=yarn density in g/cm²

ΔF=specified force difference in N

T_(t)=yarn count in tex

l₀=measuring length of the extensometer in mm

Δl=length difference of the specified force difference in mm

Results:

The results are represented graphically in FIG. 1 .

In FIG. 1 , the tensile strength in MPa is represented as a function of the intertwining of the yarns in t/m. As also described above, the first four specimens have 1 wt. % of matrix resin. The final comparative specimen is a STS40 E23 24K carbon fibre yarn from the company Teijin Carbon Europe with 1600 tex that was thoroughly impregnated with an epoxy-based resin material. The resin proportion in the yarn was 39 wt. %. The first specimen has no twisting or intertwining with OZ and reaches a tensile strength of 1955 MPa. With increasing twisting or intertwining, it can be seen that the tensile strength increases despite the same proportion of matrix resin in the fibres. With a twisting of 15Z, i.e. 15 t/m, rotated to the right, a tensile strength of 2309 MPa is achieved. There is thus an increase of around 18%, which can be attributed to the twisting or intertwining of the yarn. It is assumed that by intertwining, interlacing or twisting the carbon fibres to form the thread-like structure a cohesion of the filaments among each other can be effected similarly to the one that could be obtained by impregnation of the fibres. Due to the cohesion of the filaments among each other, the thread-like structure then achieves good tensile strengths. However, due to the very low matrix proportion of the thread-like structure, the material is particularly suitable for use as fire-resistant reinforcement. As already mentioned, high temperatures, such as those that occur in a fire, can decompose the matrix resin under gas formation. In the process, the cohesion of the filaments among each other is lost and the concrete construction part can burst. As a result, the construction part fails. With a matrix content of at most or below 5 wt. %, it can be assumed that the gas formation is not sufficient to cause damage to the construction part. In an advantageous manner, good tensile strength of the textile reinforcement with good fire resistance at the same time is thus achieved.

EXAMPLE 2

In example 2, the temperature resistance of carbon fibres is examined as a function of a vermiculite coating. The vermiculite coating represents an embodiment for the separate layer protecting against oxidation. The coating of the carbon fibre is comparable to a coating of a reinforcement, since in general the improvement of the heat resistance of the fibres from which the reinforcement is constructed can be shown by the coating.

Material:

-   -   STS40 E23 24K 1600 tex, 5Z     -   Vermiculite dispersion (AVD, manufacturer: Dupre Minerals Ltd.,         GB)     -   Single thread coating facility (unwinding stand with run-off         spindle and brake for setting the thread tension, beaker bath         for resin impregnation with adjustable beaker holder and base         plate for attaching the rolls (FIG. 3 ) and coating eyelets         (FIG. 4 ))     -   Winding board (FIG. 5 )     -   Drying cabinet with a temperature range up to at least 150° C.     -   Yarn shears     -   Steel blade     -   Plastic cutting board     -   Plastic hammer     -   Alsint dishes (H×L×W: 15 mm×200 mm×15 mm)     -   Muffle furnace with a temperature range up to at least 1000° C.     -   Scale with an accuracy of ±0.001 g

Carrying Out:

The bobbin with the intertwined thread is mounted on the unwinding stand. The yarn is guided through a beaker bath with coating dispersion to the eyelet via rollers that are easy to dismantle and clean (FIG. 3 ). The eyelet (FIG. 4 ) strips the excess dispersion from the yarn. The drive is manual by winding the yarn after the eyelet on a winding board (FIG. 5 ). A yarn brake keeps the yarn under slight tension when it is pulled off manually. In this way the yarn is continuously coated. The vermiculite coating achieved is indicated in Table 1.

TABLE 1 Vermiculite bath Eyelet diameter Achieved vermiculite concentration [%] [mm] content [%]  0 none  0    5 2.6  3.7 12 3.0 13  

For each specimen, four pieces of yarn, each 16 cm, are placed in an Alsint dish (pure CF weight approx. 1 g) and placed in a muffle furnace at room temperature. The furnace is heated to 900° C., the dishes are removed immediately when this temperature is reached and placed on a bed of sand for cooling. When the specimens have cooled back to room temperature, the total mass loss is determined by back-weighing. This is converted to the mass loss of the carbon fibre. At least one duplicate determination is carried out.

FIG. 2 represents the result of example 2.

In the case of a yarn without a vermiculite coating as a layer protecting against oxidation, the average mass loss is about 68 wt. %. In the case of a yarn with a 3.7 wt. % vermiculite coating as the layer protecting against oxidation, the average mass loss was reduced by about 11 wt. % and was still about 56 wt. %. In the case of a vermiculite coating of the carbon fibres with 13 wt. %, the average mass loss was about 30 wt. %, so that compared to the uncoated carbon fibre yarn, even a mass loss reduction by more than 50 wt. % was achieved. Thus, example 2 shows that a separate coating with a layer protecting against oxidation can also protect the carbon fibres at high temperatures, so that the carbon fibres remain temperature-resistant even in the presence of oxygen. A reinforcement that has such a separate layer protecting against oxidation thus retains its reinforcing properties even in the event of a fire, so that the construction part with the reinforcement does not fail or fails at a later point in time even in the event of a fire.

EXAMPLE 3

In example 3, a stretch body test was carried out. The fibre specimens P11 and P12 (specimen details can be found in Table 2) were embedded in concrete and the maximum load was determined by means of a tensile test.

Specimen Preparation:

After delivery, the yarn strands were stored dry at room climate until concreting. The expansion body specimens with the dimensions 800×60×15 mm³ were prepared in plastic moulds. Four test specimens were prepared standing (standing height 60 mm) for each yarn type. Each specimen contained eight strands of yarn. The target position of the yarn strands can be seen in FIG. 7 .

The specimens were prepared on three consecutive days with two sets of specimens each. Four individual specimens were prepared with one set of specimens. First, the strands of yarn were fixed in the mould by means of springs with a slight pre-tension. For fixing, the yarn strands were bent at their ends and fastened with cable ties and superglue. FIG. 8 shows the installed strands of yarn.

Ready-mixed fine concrete with a maximum grain size of 1 mm was used as the concrete (compressive strength >60 N/mm²). The dry mixture was homogenized for all concreting and then filled for the individual concreting. The dry mixture was mixed in a bucket mixer with an automatic timer according to the manufacturer's instructions. After the mixing process, two moulds per concreting were poured in less than 30 minutes under constant shaking. The test specimens were then stored covered at room climate for 20-24 hours until they were removed from the mould. After being removed from the mould, the specimens were stored in a climatic cabinet at 20° C. and >95% rel. humidity for a maximum of six days. Finally, they were stored at 22° C. and 65% rel. humidity up to the test.

Test of the Expansion Body Specimens:

The test of the expansion body specimens took place 13 or 14 days after the preparation. The tests were performed with a universal testing machine equipped with a class 1 load cell with a maximum load of 50 kN (calibrated in December 2020). For the test, the specimens were clamped in bolted steel straps over a length of 250 mm each. The steel straps are provided with compensating layers to compensate for surface inaccuracies and for secure adhesion of the specimen in the clamping area. The connection of the clamping jaws to the testing machine was realized via ball joint heads. The test setup is represented (rotated) in FIG. 9 .

Prior to the test, the test specimens were measured with regard to their geometric properties. For this purpose, the specimen width (nominal size 60 mm) and the specimen thickness (nominal size 15 mm) were determined in the area of the free stretch length at the top, middle and bottom. The measured values were within the usual tolerances. After installing the specimen, the force was tared to zero with the specimen suspended. The weight of the specimen and the lower clamp construction was approx. 65 N. The specimen was then manually brought to a preload of <150 N and the test started. The approach speed of the testing machine was 0.5 mm/min and the subsequent testing speed was 1 mm/min. If the force dropped by >90%, the test was automatically stopped. During the test, the machine path (traverse path) and the force were recorded at a measuring rate of 50 Hz.

Results:

TABLE 2 Averaged Vermi- Maximum Average Load at Mean mean culite Date of load value first Number Crack crack Fibre Yarn [wt. Specimen prep- Test Age Fmax Fmax crack of distance distance Mode of type type Turns %] name aration date [d] [N] cracks [mm] failure PU STS40 5 0 PU-A 21 Feb. 3 Feb. 13 3496 3543 3920 1 300 300 Pull-out F13 2021 2021 failure 24K P11-B 3244 3519 1 300 Pull-out 1600tex failure PU-C 3588 3783 1 300 Pull-out failure P11-D 3844 3482 1 300 Pull-out failure P12 STS40 30 0 P12-1 4820 4980 2712 2 150 138 Pull-out F13 failure 24K P12-2 5212 3690 3 100 Pull-out 1600tex failure P12-3 4762 3924 2 150 Pull-out failure P12-4 5127 3433 2 150 Pull-out failure

During the test, the number of cracks was determined in the completed crack pattern and recorded. Cracks near the jaw exits were counted, even if they were positioned slightly within the jaws. The mean values indicated (arithmetic mean) relate to 4 individual results in each case. The maximum force was determined after the first crack. The mean crack spacing (e) was determined as follows: e=L0/number of cracks with L0=free expansion length=300 mm.

In contrast to example 1, it can thus be demonstrated that the intertwined fibres have good tensile strength even when embedded in concrete without matrix impregnation. Furthermore, this example proved that the intertwining of the fibre specimens also embedded in concrete surprisingly has an influence on the tensile strength. The maximum load of the fibre specimen with only 5 turns per meter is on average a little less than 30% lower than the average maximum load of the same fibre specimen with only 30 turns per meter. The intertwining of the fibres is therefore surprisingly suitable for increasing the intimate connection of the fibres among each other, even without matrix material, and thus for improving the tensile strength of the entire composite. The results are represented in Table 2. 

1. A textile reinforcement for embedding in concrete, having carbon fibers, wherein the reinforcement is coated with a layer protecting against oxidation, wherein the carbon fibers are present as an interlaced, intertwined, twisted or cabled thread-like structure and have a maximum of 5 wt. % of a matrix resin, the layer protecting against oxidation forms a separate layer and can produce a chemical bond to a component of concrete.
 2. The textile reinforcement according to claim 1, wherein the textile reinforcement has at least one further thread-like structure.
 3. The textile reinforcement according to claim 2, wherein the further thread-like structure can contain carbon fibers, aramide fibers, polyamide fibers, AR glass fibers, polypropylene fibers, polyvinyl alcohol fibers, oxidized, infusible polyacrylonitrile fibers, polyester fibers and/or a mixture of the fiber types mentioned.
 4. The textile reinforcement according to claim 1, wherein the thread-like structure has a structured surface.
 5. The textile reinforcement according to claim 1, wherein the layer protecting against oxidation consists of at least 80 wt. % of inorganic material.
 6. The textile reinforcement according to claim 1, wherein the layer protecting against oxidation contains at least 5 wt. % of silicon.
 7. The textile reinforcement according to claim 6, wherein the layer protecting against oxidation contains silanol groups on its surface.
 8. The textile reinforcement according to claim 6, wherein the layer protecting against oxidation consists of at least 30% of silicon dioxide.
 9. The textile reinforcement according to claim 1, wherein the layer protecting against oxidation contains a phyllosilicate.
 10. Textile reinforcement according to claim 9, wherein the phyllosilicate is vermiculite.
 11. The textile reinforcement according to claim 1, wherein there is an adhesive layer between the carbon fibers and the layer protecting against oxidation.
 12. The textile reinforcement according to claim 11, wherein the adhesive layer contains organically functionalized silanes.
 13. The textile reinforcement according to claim 1, wherein the textile reinforcement has a protective layer.
 14. A concrete construction part, having a textile reinforcement according to claim
 1. 15. The concrete construction part according to claim 14, wherein the textile reinforcement has at most one concrete cover of 50 mm and has a fire resistance class of at least R
 60. 